Temperature effects on metabolism, ventilation, and oxygen extraction in a Neotropical bat.

We examined the relationship between ambient temperature (Ta), body temperature (Tb), oxygen consumption (VO2), carbon dioxide production (VCO2), evaporative water loss (mH2O), respiratory frequency (f), tidal volume (VT), minute volume (VI), and oxygen extraction (EO2) in the Neotropical bat Noctilio albiventris (mean mass 40 g). The factorial aerobic scope was 7.2 between Ta of 1-35 degrees C (VO2 = 0.119 and 0.0165 ml/(g.min), respectively). The respiratory exchange ratio (VCO2/VO2) did not change with Ta and mH2O was constant between Ta of 10-35 degrees C. Thermal conductance was minimal at 30 degrees C and constant and low at Ta less than 30 degrees C. Between 10 and 35 degrees C, Noctilio accommodated changing VO2 with parallel and roughly equivalent changes in f, VT, and EO2. The change in VO2 between 10 and 1 degrees C was accommodated mainly through changing f. Ventilation parameters in resting thermoneutral Noctilio are intermediate between allometric values for birds and mammals. Maximal EO2 in Noctilio (35-40%) is higher than for other mammals but considerably less than maximal EO2 in some birds.